Packing for the shafts of steam turbines



Patented June 16., 1936 Gustav Huhn, Berlin-Tempelhof,

' application February 9, 193s, sensi isa-.5,831 In Germany November 25,'1933 1 The invention .aims "to provide an improved packing for theshafts of high-pressure steam.

' .bearing rings.

turbines, 4the packing beingof a type in whichn the shaft carriesannular ribs having knife-like outer peripheral edges cooperable withthe inner peripheral surfaces of bearing rings carried by the casing.The ribs are formed of metal having substantially the same coeilicientof thermal expansion as the shaft, and the rings which cooperate withthe-outer peripheral edges of said ribs are formed of a relatively softmaterial having a lower coefficient of thermal expansion than saidribs,whereby these ribs when expanded will cut individual paths in theinner surfaces of the The bearing rings preferably consist of a mixtureof graphite-carbon and a liquid or semi-liquid fixing agent and saidrings will not, therefore. expand materially upon increase in thetemperature of the shaft. These rings may well. consist of a mixture .ofcarbon. graphite and liquid synthetic resin, the mixture beingintroduced intodove-tail annular grooves ofthe casing in a plastic stateand being subsequently solidified by heating. Owing to this spcial wayof forming and attaching the bearing rings, they are immovably held evenat high temperatures of the turbine and will not therefore becomeloosened.

The drawing illustrates a longitudinal sectional view partlyinelevation, of a packing constructed in accordance with the invention. I

The turbine shaft is illustrated at I-, and denotes a portion of theturbine casing surrounding said shaft. Annular ribs` 2 are integral withor otherwise secured to the shaft I, said ribs having substantially thesame coemcient of expansion as said shaft. The outer peripheral edges 3of these ribs `2 are knife-like so that each rib edge forms a smoothcircular line. The'cas'ing 5 is grooved to looselyreceive the ribs 2 andthe botI tom of each groove 4 is of dove-tail cross sec-v tion, and ineach of th'ese dove-tail groove portions, a bearing ring 1 is securelyheld, said bearing ring preferably consisting of the above-mentionedmixture placed in position in al plastic l state and solidified byheating. 'I'he number of ribs 2. bearing rings 1 and grooves I isdetermined'by the pressure used in operating the turbine.. In thepresent disclosure, twelve of each, with the grooves Q separated bynarrow webs 8, are illustrated. l I The packing effect is obtained bysubstantially aline packing. During the trial runs of the turbine.. eachannular rib! will cut its path on the relatively soft bearing ring orlining I even if anonima. (o1. aac-16) axial motions of the shaft occur,and any slight irregularities in the circular contour of the ribs 2,will produce extremely narrow and shallow grooves or scores in thebearing surfaces, causing the entire packing to act similarly to aconven- 5 tional labyrinth packing, with the dierence however, that thegrooves or'scores in the bearing surfaces will be infinitely iin er thancould be obtained in a labyrinth packing consisting of metal webs.

The improved packing allows a contact between the edges gliding touch orof the ribs 2 and the rings or linings 1, subsequent to the grinding-inwhich occurs during the trial runs, and no appreciable friction willtake place, particularly if the edges of the ribs 2 have been ground anda graphite-carbon material has been used for each lining or bearingsurface. J The improved packing requires, when oompared with theordinary labyrinth packings, a

much shorter length, and a number ofannular ribs and bearing surfaceswill comparatively small sufllce to bring about the desired end. Thepackling may be applied to all kinds of steam turbines and othercentrifugal machines and to` all revolving parts of such machines.rangement shown, even when used in connection Although the arwithcomparativel'yhigh-speed pressures, produces a reliable packing, it1 mayunder certain conditions proveo'f advantage to combine said packing 30with one of some other type, for instance, an ordix nary labyrinthpacking.

I claim:-

1. A packing 'for a steam ing circumferential annular ribs connectedl'ildlirV 35 turbine shaft compriswith the shaft and formed from a metalhaving a coefficient of thermal expansion similar to said shaft, saidribs having circular knife-shaped outer vided with bearing ringssurrounding and co-axperipheral edges, the turbine casing being proingrings.

2. A structure as .specified in claimr 1; the tur- *50 bine casingbeingprovided with circular grooves of dovetail cross section in which saidbearing rings are snugly held, said bearing rings being composed ofl aheat-solidified material.

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